Cup-point fastener

Claim 1

A fastener pin having a cylindrical body portion for engaging the wall of a bore extending through a first member and having a cup-point at one of its ends integrally formed therein for engagement with and penetration into the surface of a second member for preventing relative movement between said members when said fastener pin is inserted through said bore and is in engagement with and penetrating into said surface, said cup-point having an outer flank continuously curving downwardly and inwardly and an inner flank continuously sloping downwardly and outwardly which meet and terminate in a surface engaging and penetrating edge extending circularly around and spaced radially outwardly from the vertical axis of said pin, said curving outer flank and said inner flank forming therebetween a wedge extending upwardly from said edge, said wedge progressively increasing in thickness upwardly from said edge, the ratio of the thickness of the inner wedge segment to the thickness of the outer wedge segment, when said wedge is divided by a line parallel to the pin axis and passing through the inner and outer flank intersection point, increasing by about 20% when measured in planes parallel to the plane of said edge at intervals of 20% between said plane of said edge and a plane parallel to said edge at a distance from said edge plane about 20% of the diameter of said cavity opening when measured beginning at said surface engaging and penetrating edge, the thickness of the inner and outer wedge segments in said plane at a distance from said edge plane of about 20% being substantially equal and the combined thickness of said segments being substantially equal to the distance of said plane from said eDge plane.